Vitesse radiator cap

[Gadgetman]

What psi radiator cap should a Vitesse 6 have (without separate header tank) I’ve a 7psi cap but it never vents to the overflow  bottle no matter how hot the engine gets even if the,radiator is brimmed full when the engine is cold....

[johny]

I believe thats the right cap and if the level in the overflow bottle never increases as the engine heats up you must have something else in the system that is absorbing the slight increase in the volume of the water as its temperature increases (about 400cc?). This expansion must be absorbed somewhere or something would burst so either you have a leak, air in the system or hoses so flexible they stretch to do the job!

[Gadgetman]

1 minute ago, johny said:

I believe thats the right cap and if the level in the overflow bottle never increases as the engine heats up you must have something else in the system that is absorbing the slight increase in the volume of the water as its temperature increases (about 400cc?). This expansion must be absorbed somewhere or something would burst so either you have a leak, air in the system or hoses so flexible they stretch to do the job!

Well there are certainly no leaks and I’ve bled the system thoroughly so it must be the new hoses expanding to take up the increased volume! I wonder if the cap is faulty ( pattern parts?) or is too long for the radiator neck so it’s already partly compressing the cap spring. Does anyone know what length the cap should be ( underside to bottom Of rubber seal on spring)

[johny]

As I say it doesnt matter what resistance to opening th cap has the water expansion will overcome it (or split something else) so as nothing has broken the increase in volume must be absorbed somewhere...

I take it your heater works well? If not this is the most likely place for an air pocket.

[johny]

I see what you mean, if the cap was a real struggle to put on it could have a higher opening pressure so making the hoses stretch excessively? I think it would show as the hoses would look quite swollen...

[Pete Lewis]

7 psi is correct    it needs the secondary cap seal uder the cap to seal the filler neck or any shift to the bottle will fail

whilst there are two cap depths  i doubt you will fit a deep cap to a shallow neck where as its easy to fit a shallow cap to a deep neck

I take it your car does not have the remote header tank ???   

Pete

[Gadgetman]

4 minutes ago, Pete Lewis said:

7 psi is correct    it needs the secondary cap seal uder the cap to seal the filler neck or any shift to the bottle will fail

whilst there are two cap depths  i doubt you will fit a deep cap to a shallow neck where as its easy to fit a shallow cap to a deep neck

I take it your car does not have the remote header tank ???   

Pete

Hi Pete, nope no remote header  just the std later rad with overflow bottle

 

 

[johny]

1 hour ago, Gadgetman said:

What psi radiator cap should a Vitesse 6 have (without separate header tank) I’ve a 7psi cap but it never vents to the overflow  bottle no matter how hot the engine gets even if the,radiator is brimmed full when the engine is cold....

You say here 'even if the radiator is brimmed' - it should already be full to the top every time you take the cap off, without fail. Also the overflow pipe, with its end permanently submerged, is a syphon so must always be full. 

If you dont find them like that then you have lost water from the system and it hasnt been replaced with water from the overflow bottle. This can be a leak which is sometimes so small  the water escapes as steam and you never see it and then, on cooling, air is drawn in because thats easier than pulling water back from the overflow. Ive really struggled to find these leaks sometimes and they usually turn out to be where hoses clamp on to components.

Another possibility is a leak in the overflow pipe so that water flows out ok but air is drawn back which is why it should be clamped tight to the radiator vent pipe.

In either case once you have an air pocket in the top of the radiator water will no longer be expelled to the overflow bottle. Sometime the system can then operate quite happily like a modern sealed system but of course you run the risk of reduced cooling because some radiator tubes might not be getting a flow...  

[Gary Flinn]

All Vitesse and Herald models up to around 1970 should have 7 PSI Caps, then I have read they standardised on 13 PSI on a number of cars, Heralds/Vitesse/Spitfire/GT6 I believe?

Are you making sure the Overflow bottle is half full of coolant?

Regards

Gary 

 

[Gadgetman]

25 minutes ago, Gary Flinn said:

All Vitesse and Herald models up to around 1970 should have 7 PSI Caps, then I have read they standardised on 13 PSI on a number of cars, Heralds/Vitesse/Spitfire/GT6 I believe?

Are you making sure the Overflow bottle is half full of coolant?

Regards

Gary 

 

Thanks

its not half full but the end of the pipe is submerged (1/3 full)

[Pete Lewis]

just a thought  it does have a 82c thermostat   as if it doenst get very hot it wont expand any coolant out 

and what ever goes on if you are not loosing coolant on a run   whats the problem is there really a problem 

if the overflow shows of little use 

i would drive smile and sleep easy on this and the Vit6 doesnt need to be brimmed  a air gap is really pretty normal 

just keep an eye on the level is not constantly in need of the top up

 

Pete

[Ian Foster]

Gadgetman

If you are not getting any flow into the expansion bottle and you cannot see any obvious leaks, I would suggest that there must be an airlock somewhere in the system and this is 'absorbing' the expansion. The level in my expansion bottle typically rises and falls by 50mm between fully cold and hot.

I have emptied and refilled my system a few times recently, fighting a bottom hose sealing problem (now hopefully sorted) and have developed a procedure that seems to work well for me. I have been meaning to do a write up for Cookie's GT6 register page. Picture attached of my refill/bleed technique, which is a home built version of a commercial fill funnel which are typically £40+.

• open heater valve (check the valve is actually opening fully)
• drain out the the fluid using the tap on the bottom of the rad (could be a good time to flush and replace the antifreeze, in which case I would also open/remove the tap on the rear of the block and do all of the poking around thing)
• make a wide funnel using a juice bottle or similar connected via a short length of clear pipe to rubber bung fitted into the radiator neck. I have used a bung from a wine brewing kit, drilled out to suit. The bung seals into the lower part of the filler neck and stops fluid getting to the overflow pipe. Support the funnel so that it can't topple, I tied it up to the bonnet. (I have actually added a couple of hose clamps to the set up as shown as the pipe softens a bit as it gets hot)
• refill the system 'very slowly' via the funnel until the level rises into the funnel
• I do actually have a bleed point in the thermostat housing, which is a remnant of a previous header tank experiment and this helps to bleed air out as you fill. I close this off before I start the car as the the thermostat housing will be pressurised by the pump before the thermostat opens
• I then start the car and let it come up to temperature, feeling the various hoses and the top and bottom of the radiator to monitor progress
• repeatedly squeezing the top and bottom hoses helps to move any trapped air once the system is starting to circulate. This takes a while
• during this process you will see air expelled into the funnel in various burps and glugs and the level will rise and fall. I don't let it get more than about 1/3rd full, drawing off any excess with a large syringe
• I would typically turn of the engine off at least once to let things cool a little and settle down
• allow the engine to get fully up to temperature on the gauge, which for me means allowing the electric fan to cycle on and off a couple of times
• I then let the engine cool and add more fluid into the funnel as required, so there is always a head above the level of the radiator cap.
• I then open my bleed on the thermostat housing to make sure there isn't any trapped air and then finally reduce the level in the funnel/pipe so I can refit the radiator cap

One thing to check to ensure the overflow bottle can function correctly is that the top of the radiator neck is a fair surface suitable for the top seal of the cap to mate onto. A pass with some fine wet and dry on a flat pad will show whether it is flat. If this doesn't seal there won't be sufficient vacuum to pull back expelled fluid from the overflow bottle (article in GT6 Register No. 484 October 2020).

Hope this helps

Ian

[Pete Lewis]

luckily on the Vitesse /Herald the rad is not as below the head height like the GT6 

a refill with the engine idling fast is always a good plan 

we seen GT6 up on ramps and kerbs to raise the front in efforts to refill  without air locks  . they are not straight  forward

the other cars are much easier , a quick release of a heater hose will expel most trapped air locks 

an air lock will expand the air volume on heating up and that pushes the coolant out the overflow  if there are no leaks and a bit of sherlock doesnt find 

any coolant loss ,  dont worry 

Pete

 

 

[Chris A]

2 hours ago, Gary Flinn said:

All Vitesse and Herald models up to around 1970 should have 7 PSI Caps, then I have read they standardised on 13 PSI on a number of cars, Heralds/Vitesse/Spitfire/GT6 I believe?

For Heralds my book confirms 7 lb for 948, 1200 & 1250s from engine N° GA.240782.E 13 lb. 13/60 7 lb and from engine N° GE.22521.E 13 lb. My 13/60 from 1968 has the 13 lb, engine N° is after the cutoff I believe it to be the original.

As for water level it says to fill to 1" below the filler neck to allow for expansion. Of course the 13/60 doesn't have the overflow bottle.

[Ian Foster]

1 hour ago, Pete Lewis said:

luckily on the Vitesse /Herald the rad is not as below the head height like the GT6 

Indeed. The GT6 poses some unique challenges.

Ian

[daverclasper]

I had this happening and it was all the sealing issues mentioned above. The cap was not sealing on lower rad neck flange as the cap was too short. Made up a seal and spacer washer.  Top of filler neck was not flat, so a gentle flat with wet and dry on a block. Hose was not air tight at filler neck.

After sorting, the system took about an extra 750ml of coolent and car runs a bit cooler around town. Also no air in system, which is better for corrosion I guess.

So no massive deal, but didn't cost anything either.

Dave

 

 

 

Edited May 17, 2021 by daverclasper